Including source code for MODULE PROCEDURES when `source: true`

I have noticed that, when the implementation of a MODULE FUNCTION or a MODULE SUBROUTINE, whose interface is in MODULE foo, is done in a SUBMODULE of MODULE foo using the statement MODULE PROCEDURE, the source code of the procedure is not included in the documentation, even though `source: true`.

I have tried to use the statement MODULE FUNCTION in the implementation (which forces me to redeclare the arguments and the result of the function, so I would really like to avoid that) and the source code appears in the documentation.

As a feature request, can the source code be included in the documentation even when using MODULE PROCEDURE?